1. Field of Invention
The present invention relates to a GPS module test system, and more particularly to a GPS module test system for automatically calibrating a test signal.
2. Related Art
Global position system (GPS) is a kind of technology for precisely positioning the coordinates of an object, such as a vehicle or a ship. The earlier GPS technology was developed by the United States Department of Defense for military purposes. Now, the GPS technology switches to civil applications from the military fields, for example, map navigation. Some electronic equipments, such as personal digital assistants (PDAs), computers, mobile phones, and watches, are all provided with a micro GPS module, such that the navigation function of the electronic equipments can be used anywhere at anytime. A GPS module includes an antenna, an RF, and an analog-to-digital converter (ADC). After the antenna receives a weak signal transmitted from a GPS satellite, the signal is amplified to an appropriate extent by an RF component. Subsequently, the frequency is reduced to an intermediate frequency (IF) band or a baseband. Afterward, the ADC component converts analog signals into digital signals, and then desired information such as coordinates and time are resolved from the digital signals.
However, since the GPS signal is a quite weak satellite signal, production problems must be taken into consideration on the design of the GPS module, so as to make sure that the designed/produced GPS module is usable (i.e., the GPS module is able to correctly receive and resolve a weak GPS signal). In order to ensure the signal resolution accuracy and the usability of the GPS module, GPS module test becomes a critical step in manufacturing the GPS module. At present, a common method of testing a GPS module is to first weld the GPS module onto a test board, and then test the GPS module with a test program provided by a GPS module manufacturer. Thus, the welding quality may directly influence the test quality of the GPS module (affecting the receiving power of the GPS module, and thus reducing the db value thereof). In addition, a tester is unable to control a satellite signal simulator to adjust the RF power, and a test fixture does not have the function of auto calibration (i.e., to confirm that the sensitivity of this test is the same as that of the previous one). Further, the conventional test fixture does not have the function of automatically determining pass/failure (i.e., automatically determining whether the GPS module is qualified), and cannot test GPS modules repeatedly. Thus, when another GPS module is to be tested, the previously tested GPS module must be disordered first, and then the GPS module under test is welded, so the operation is rather troublesome.